Hydraulic characteristics of typical bank‐protection works along the <scp>B</scp>rahmaputra/<scp>J</scp>amuna <scp>R</scp>iver, <scp>B</scp>angladesh

Nakagawa, Hiroji; Zhang, H.; Baba, Yasuyuki; Kawaike, Kenji; Teraguchi, Hiroshi

doi:10.1111/jfr3.12021

Cited by 36 publications

(13 citation statements)

References 17 publications

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“…In the slit-type spur case, at the same location, the transverse velocity component, v, becomes 0.61 m/s, and in the impermeable spur case, it becomes −1.71 m/s. Such a strong recirculating velocity was also observed [4] in the real field. Researchers [62] also concluded that in the dead zones of impermeable spur-like structures, the main transport mechanism is transverse turbulent diffusion which controls the exchange processes with the mainstream.…”

Section: Application Of Slit-type Spurs In the Brahmaputra-jamuna Riversupporting

confidence: 76%

“…The rapid change in braided channel geometry triggers variations in the flow boundary conditions and the hydraulic structures, and changes are considered the key management issues for dynamic alluvial rivers worldwide, particularly the Brahmaputra-Jamuna River [3,4]. Several countermeasures are generally used to protect the river banks, e.g., revetment with rip rap made of different materials and the establishment of hardpoints (heavy-duty embankments) and permeable and impermeable spurs [4,5]. Previous studies have shown that almost all types of structures are partly or totally damaged when exposed to the main channel [6].…”

Section: Introductionmentioning

confidence: 99%

“…However, spur-type structures experienced frequent and severe damage compared to other high-cost river training structures, e.g., long embankments, due to the dynamic characteristics of the river and instability of the flows (governed by local scouring) induced by the structures [6,7]. Around the world, previous studies documented the use of spur dikes in rivers to provide adequate depth, mitigate bank erosion, and improve land reclamation and ecological richness by creating stagnant zones [4,6,[8][9][10][11][12][13][14][15][16][17][18]. However, field observations and multiple laboratory studies have revealed relatively large scour holes produced by impermeable spur dike fields.…”

Section: Introductionmentioning

confidence: 99%

“…Figure 1d gives no indication of very high flow velocities near the structure, but the structure still failed. A previous study [4] analyzed the failure cases of different types of structures in this river and found that the transverse flow generated due to spur-type structures has the potential to create local scouring, which is frequently ignored during dike design. The local vortex at the structure tip also plays a significant role in creating local scour.…”

Section: Introductionmentioning

confidence: 99%

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Three-Dimensional Flow Characteristics in Slit-Type Permeable Spur Dike Fields: Efficacy in Riverbank Protection

Shampa

Hasegawa

Nakagawa

et al. 2020

Water

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This paper focuses on finding efficient solutions for the design of a highly permeable pile spur (or slit type) dike field used in morphologically dynamic alluvial rivers. To test the suitability of different arrangements of this type of permeable pile spur dike field, laboratory experiments were conducted, and a three-dimensional multiphase numerical model was developed and applied, based on the experimental conditions. Three different angles to the approach flow and two types of individual pile position arrangements were tested. The results show that by using a series of slit-type spurs, the approach velocity of the flow can be considerably reduced within the spur dike zone. Using different sets of angles and installation positions, this type of permeable spur dike can be used more efficiently than traditional dikes. Notably, this type of spur dike can reduce the longitudinal velocity, turbulence intensity, and bed shear stress in the near-bank area. Additionally, the deflection of the permeable spur produces more transverse flow to the opposite bank. Arranging the piles in staggered grid positions among different spurs in a spur dike field improves functionality in terms of creating a quasi-uniform turbulence zone while simultaneously reducing the bed shear stress. Finally, the efficacy of the slit-type permeable spur dike field as a solution to the riverbank erosion problem is numerically tested in a reach of a braided river, the Brahmaputra–Jamuna River, and a comparison is made with a conventional spur dike field. The results indicate that the proposed structure ensures the smooth passing of flow compared with that for the conventional impermeable spur structure by producing a lower level of scouring (low bed shear stress) and flow intensification.

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Section: Application Of Slit-type Spurs In the Brahmaputra-jamuna Riversupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Three-Dimensional Flow Characteristics in Slit-Type Permeable Spur Dike Fields: Efficacy in Riverbank Protection

Shampa

Hasegawa

Nakagawa

et al. 2020

Water

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“…Sediment transport in the Brahmaputra River is controlled by the monsoon climate, which explains the large depositional fluctuations within the braided channel system (Roy and Sinha 2014). These regular changes in the river morphology make efficient livelihood and agricultural practices difficult, and bank stabilization is a high priority in the region (Nakagawa et al 2013). However, fixating the river width with embankments to secure floodplain communities would result in higher velocities and increased scour and erosion from a smaller cross-sectional area.…”

Section: Discussionmentioning

confidence: 99%

Present to future sediment transport of the Brahmaputra River: reducing uncertainty in predictions and management

et al. 2016

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The Brahmaputra River in South Asia carries one of the world's highest sediment loads, and the sediment transport dynamics strongly affect the region's ecology and agriculture. However, present understanding of sediment conditions and dynamics is hindered by limited access to hydrological and geomorphological data, which impacts predictive models needed in management. We here synthesize reported peer-reviewed data relevant to sediment transport and perform a sensitivity analysis to identify sensitive and uncertain parameters, using the one-dimensional model HEC-RAS, considering both present and future climatic conditions. Results showed that there is considerable uncertainty in openly available estimates (260-720 Mt yr -1 ) of the annual sediment load for the Brahmaputra River at its downstream Bahadurabad gauging station (Bangladesh). This may aggravate scientific impact studies of planned power plant and reservoir construction in the region, as well as more general effects of ongoing land use change and climate change. We found that data scarcity on sediment grain size distribution, water discharge, and Manning's roughness coefficient had the strongest controls on the modelled sediment load. However, despite uncertainty in absolute loads, we showed that predicted relative changes, including a future increase in sediment load by about 40 % at Bahadurabad by 2075-2100, were consistent across multiple model simulations. Nevertheless, for the future scenarios we found that parameter uncertainty almost doubled for water discharge and river geometry, highlighting that improved information on these parameters could greatly advance the abilities to predict and manage current and future sediment dynamics in the Brahmaputra river basin.

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The Jamuna–Brahmaputra River, Bangladesh

et al. 2022

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Bangladesh is dominated by three great rivers -the Jamuna-Brahmaputra, Ganga and Meghna -that combine to feed sediment into one of the World's largest deltas in the Bay of Bengal (Figure 21.1). Bangladesh has been shaped by, and is dependent upon, its rivers, which provide fertile soils and a diverse flora and aquaculture but also bring significant flood hazard and risk to infrastructure for a large and growing population. Current anthropogenic stresses, in terms of changing climate, water diversions, pollution and sediment extraction, are posing new pressures to the river and its inhabitants (Best, 2019). The people of Bangladesh have adapted their lifestyle for centuries to live with river flooding -frequently moving their temporary bankside homes, planting on newly emergent river bars, and sometimes raising their homesteads above water level in flood periods (Paul, 1997). However, a growing population, coupled with the expansion of infrastructure and economic development, has resulted in an increase in the intensity of flood damage (FPCO, 1995;Paul, 1997; CPD, 2004). The lives of many millions of Bangladeshi citizens are reliant on these rivers, with up to 2.3 million people living on the riverine islands alone (Schmuk-Widmann, 2001). Bangladesh's rural economy relies upon annual 'normal' floods to bring moisture and fresh sediments to the floodplain soils (Paul, 1997): for instance, two of the three seasonal rice varieties (aus and aman) cannot survive without floodwater and the fish caught both on the floodplain during flood season and from the many floodplain ponds ('beels') provide the main source of protein for many rural populations (Chowdhury, 1994;Paul, 1997; de Graff, 2003;Shankar et al., 2004). However, the effect of 'abnormal' floods can be devastating and result in appreciable damage to crops and houses, severe bank erosion with consequent loss of homesteads, schools and land, and loss of human lives, livestock and fisheries (BDER, 2004;Shankar et al., 2004). For example, in the 1998 flood, over 70 % of the land area of Bangladesh was inundated, affecting 31 million people and 1 million homesteads (Chowdhury, 2000). The 1998 flood, which had an unusually long duration from July to September, claimed 918 human lives and was responsible for damaging 16 000 and 6000 km of roads and embankments, respectively, and affecting 6000 km 2 of standing crops (Chowdhury, 2000). In the 2004 floods, over 25 % of the population of Bangladesh, or 36 million people, was affected by the floods; 800 lives were lost; 952 000 houses were destroyed and 1.4 million badly damaged; 24 000 educational institutions were affected, including the destruction of 1200 primary schools; 2 million government and private tubewells were affected, and over 3 million latrines were damaged or washed away, this increasing the risks of diarrhoea, cholera and other waterborne diseases. Also, 1.1 million ha of rice crop was submerged and lost before it could be harvested, with 7 % of the yearly aus (early season) rice crop lost; 270 000 ha o...

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Hydraulic characteristics of typical bank‐protection works along the Brahmaputra/Jamuna River, Bangladesh

Cited by 36 publications

References 17 publications

Three-Dimensional Flow Characteristics in Slit-Type Permeable Spur Dike Fields: Efficacy in Riverbank Protection

Three-Dimensional Flow Characteristics in Slit-Type Permeable Spur Dike Fields: Efficacy in Riverbank Protection

Present to future sediment transport of the Brahmaputra River: reducing uncertainty in predictions and management

The Jamuna–Brahmaputra River, Bangladesh

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